1. Field of Invention
This invention relates generally to a heat dissipating device for cooling semiconductor components which have higher heat dissipation density.
2. Description of the Prior Art
The development of microelectronics or semiconductor industry has brought us CPU, e.g. Pentium, which integrated more than a few millions transistors in one chip. Also, those CPU's plus other IC's can be integrated together into a module called as Multi-Chip Module (MCM). Those CPU or MCM have higher heat dissipation density, which suggests that the heat have to be taken away quickly in certain way, otherwise, reduce the reliability and the life.
For those obvious reasons, a passive cooling structure already on market as shown in FIG. 1. For higher heat dissipating density, a typical active cooling structure is shown in FIG. 2. An axial fan is mounted on the top of a heat sink, the heat sink is mounted in contacted with CPU chip.
Summarized prior arts, there are two major categories to pursuit more efficiency and lower profile fan cooling assembly structure. In the first category, it is to design very slim fan structure with a standard heat sink. Those designs usually lead lower efficiency and Cubic Feet per Minutes (CFM). In second category, it is to design some special heat sinks, which can have a modified axial fan sit into the heat sink. Those designs reduce the dimension in high of cooling assembly as much as the thickness of fan, but sacrifice the conductive heat dissipation of heat sink, since reduce of fin surface area. Same as the first category, it leads lower CFM. In prior arts, there are some controversies among those efforts to reach following three objects at same time: the first is the higher efficiency of air moving away from heat sink; the second is the lower profile of fan and heat sink assembly; the third keeps the higher efficiency of heat sink in both conductive and convective heat transfer. Therefore, all prior arts on cooling CPU have following disadvantages:
(a) All axial fans have hubs, which do nothing with cooling. When set the fan on the top of heat sink to suck or blow air away, the area covered by the hub, almost no air circulation happens there compared with outside of the hub. However, the hub faces often the hottest spot of semiconductor components. The hub contributes nothing of the convective heat transfer. PA1 (b) All axial fans force the air circulation motion in the heat sink in turbulent form, but the heat sink designs do not match the kind of air movement pattern well to maximize the efficiency of convective heat transfer. Inversely, it blocks the air motion, reduces air velocity. PA1 (c) Even many prior arts related to modify the heat sink or the axial fan to reduce the profile of cooling assembly, in any circumstance, anything, such as a plate, can not be set on the top too close to the fan inlet or outlet. Otherwise, no air will get in or out the heat sink. This means that this kind of cooling assembly, an axial fan and a heat sink, have the limitation in some applications, particularly in critical profile limitation. PA1 (a) to provide an air flow direction parallel to heat sink fin or air movement pattern, which perfectly matches the structure of heat sink. At same time, it increases the cooling efficiency; PA1 (b) to provide a simple combination structure of a cross flow fan and a heat sink which makes it easily mount and change orientation; PA1 (c) to provide a cooling assembly structure which can be used in various slim designs, such as notebook computer and plug-in module board; PA1 (d) to provide a cooling assembly structure which maximize the cooling efficiency in both convective and conductive heat transfer; PA1 (e) to provide a cooling assembly structure which maximizes the compatibility with those standard heat sinks available on the market; PA1 (f) to minimize the profile of the fan heat sink assembly.